Pylon mounted tilt rotor

ABSTRACT

A tilt rotor system, comprising: a pylon portion that includes: an upper protrusion that is configured to be in contact with an upper surface of a wing and a lower protrusion that is configured to be in contact with a lower surface of the wing; and a rotor portion that includes a rotor, wherein the rotor portion is able to move between: (1) a first position that is associated with a vertical flight mode and (2) a second position that is associated with a forward flight mode. The pylon portion further includes an air intake vent, a horizontal surface, a rotor controller, and a heat sink.

BACKGROUND OF THE INVENTION

New types of electric aircraft are being developed for use in urbanenvironments. For example, electrical vertical takeoff and landing(eVTOL) vehicles are attractive because they do not require a longrunway. Instead, such eVTOL vehicles can take off from and/or land inrelatively small spaces, such as parking lots, building rooftops, orother open spaces in urban environments. In some cases, these eVTOLvehicles have a relatively unique combination and/or arrangement ofcomponents or parts. As a result, new types of vehicle componentsassociated with these new types of eVTOL vehicles may be developed. Forexample, as a vehicle goes through developmental versions, improvedcomponent embodiments (e.g., to reduce assembly time of the vehicle as awhole and/or to improve the structural integrity and/or airworthiness ofthe vehicle) may be developed.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a diagram illustrating an embodiment of an electric verticaltakeoff and landing (eVTOL) vehicle with tilt rotors.

FIG. 2A is a diagram illustrating an embodiment of a tilt rotor systemprior to attachment to a wing.

FIG. 2B is a diagram illustrating an embodiment of a wing prior toattachment of a tilt rotor system.

FIG. 2C is a diagram illustrating an embodiment of a top view of a mainwing with tilt rotors attached.

FIG. 2D is a diagram illustrating an embodiment of an angled view of amain wing with tilt rotors attached.

FIG. 3A is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a forward flight position.

FIG. 3B is a diagram illustrating an embodiment of a tilt rotor system,including ductwork and streamlines, in a forward flight position.

FIG. 3C is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a forward flight position viewed at an angle.

FIG. 4A is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a vertical flight position.

FIG. 4B is a diagram illustrating an embodiment of a tilt rotor system,including ductwork and streamlines, in a vertical flight position.

FIG. 4C is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a vertical flight position viewed at an angle.

FIG. 5A is a diagram illustrating an embodiment of a tilt rotor systemwith an intake air vent on the top surface of the pylon.

FIG. 5B is a diagram illustrating an embodiment of a tilt rotor systemwith components horizontally attached inside the pylon.

FIG. 5C is a diagram illustrating an embodiment of a tilt rotor systemwith components horizontally attached inside the pylon and streamlinesshown.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Various embodiments of a tilt rotor system that is used in an electricvertical takeoff and landing (eVTOL) vehicle are described herein. Aswill be described in more detail below, in various embodiments, the tiltrotor examples described herein show various features that improve theassembly of the vehicle (e.g., the tilt rotor is able to be attached ina more secure manner to the wing), improve the structural integrity orairworthiness of the vehicle, and/or optimize the heat dissipation ofthe electrical components within the pylon portion of the tilt rotor.However, before such examples are described, it may be helpful to showan example of an eVTOL vehicle which includes such a tilt rotor. Thefollowing figure describes one such exemplary eVTOL vehicle.

FIG. 1 is a diagram illustrating an embodiment of an electric verticaltakeoff and landing (eVTOL) vehicle with tilt rotors. In the exampleshown, the vehicle (100) includes six tilt rotors (e.g., 102) which areattached to a forward-swept main wing (104) and two tilt rotors (e.g.,106) which are attached to a canard (108). All of the tilt rotorsinclude a pylon portion (e.g., 110 and 112) via which the tilt rotorsystem is attached to the wing or canard. This pylon portion does notmove when the moveable rotor portion of the tilt rotor system (e.g., 114and 116) tilts between a downward pointing position (e.g., when thevehicle is operating in a hovering and/or vertical flight mode which isnot shown here) and a backward pointing position (e.g., when the vehicleis operating in forward flight or wing-borne flight mode which is shownhere). For context, the vehicle measures within a range of 3-6 metersfrom nose to tail with a wingspan within a range of 6-8 meters.

In one example flight sequence, the vehicle takes off vertically byorienting all of the tilt rotors to point downward and then using thetilt rotors to provide vertical thrust and lift. This may be attractivein urban areas because the vehicle's takeoff and landing footprint ismuch smaller than conventional takeoff and landing vehicles whichrequire a long runway.

Once the vehicle has taken off and has achieved some desired altitude,the vehicle transitions to a forward flight mode by rotating the tiltrotors so that they point backwards and produce horizontal thrust. Thetilt rotors may be rotated using a variety of actuators and anyappropriate actuator may be used. This forward flight mode is attractivebecause it is much more energy efficient to fly using wing-borne flightcompared to relying on the tilt rotors to generate all of the verticallift required to keep the vehicle airborne. In some embodiments, one ormore of the tilt rotors are turned off when in forward flight mode toconserve power if not all of the tilt rotors are required to be rotatingin order to keep the vehicle airborne.

To land (in this example, vertically), the tilt rotors are rotated sothat they point downward once again so that the vehicle hovers in air.The vehicle then vertically descends to a landing point on the ground.If needed, any tilt rotors that were turned off during forward flightmode are turned on. As described above, the vehicle's ability to takeoff and land vertically is desirable because the vehicle can land in asmaller area or footprint. However, if desired, the exemplary vehiclecan perform a traditional landing (which would require a runway) bykeeping the tilt rotors in the forward flight position (i.e., pointingbackwards as shown here) and using the exemplary skids (118) or wheels(not shown here) to land.

The combination of a canard and forward-swept main wing (as shown inthis example) is attractive because of its performance, for example, inthe event of a stall. The canard will stall first before the main wing,creating a significant pitching moment and not much loss of lift atstall whereas a main wing stall loses significant lift per change inpitching moment (e.g., causing the entire aircraft to drop or fall).Stalls are thus potentially more benign with a canard compared towithout a canard. The canard stall behavior is particularly beneficialin combination with a swept forward wing, as the stall of the main wingcan create an adverse pitching moment if at the wing root and can createlarge and dangerous rolling moments if at the wing tip. Furthermore, acanard can create lift at low airspeeds and increase CL_(max) (i.e.,maximum lift coefficient) and provides a strut to hold or otherwiseattach the canard tilt rotor systems to.

Another benefit to using pusher-style (i.e., attached to the trailingedge of the main wing) tilt rotor systems with a fixed (main) wing asshown here is that stall behavior (or lack thereof) is improved duringthe transition from hover position to cruise position or vice versa.With a tilt wing vehicle (which was tested in an earlier prototype), thewing's angle of attack (and subsequently forces on the wing) undergolarge, discontinuous changes as the wing tilts from a completely stalledcondition to an unstalled condition. In contrast, with the vehicle shownin this example, the vehicle can be flown such that the wing angle ofattack does not increase beyond the stall angle. Also, thisconfiguration adds both dynamic pressure and circulation over the mainwing, which substantially improves the behavior during a transition(e.g., from hover position to cruise position or vice versa). In otherwords, the total time for transition can be reduced and transition canbe more efficient and be performed at lower airspeeds, leading toincreased safety.

Another benefit associated with tilt rotor vehicles (e.g., as opposed totilt wing vehicles) is that a smaller mass fraction is used for the tiltactuator(s). That is, multiple actuators for multiple tilt rotor systems(still) comprise a smaller mass fraction than a single, heavy actuatorfor a tilt wing vehicle. There are also fewer points of failure withtilt rotor vehicles since there are multiple actuators as opposed to asingle (and heavy) actuator for a tilt wing vehicle. Another benefit isthat a fixed wing vehicle makes the transition (e.g., between a cruisingmode or position and a hovering mode or position) more stable and/orfaster compared to a tilt wing vehicle.

The example vehicle shown here is a relatively new vehicle that has gonethrough multiple development cycles. In an earlier version of thevehicle, the inboard, main-wing tilt rotors (e.g., the ones not locatedat the tips of the canard and main wing) were attached to the trailingedge or surface of the main wing by first cutting out an ellipticalshape in the main wing. The elliptically-shaped distal end of the pylonportion would then be inserted into the similarly shaped cutout and thentwo parts would be attached (e.g., using adhesives, by applying aflexible material over the surfaces of both the pylon portion and themain wing, etc.).

One disadvantage is the resulting structural integrity and/orairworthiness of the vehicle may be less than desired. For example, thevehicle may be able to fly and/or maneuver at relatively high speeds(e.g., on the order of 150-200 knots), subjecting the vehicle torelatively high forces and/or moments. New tilt rotor components which,when attached to the vehicle, produce a vehicle with better structuralintegrity would be desirable. As with any aircraft, improving structuralintegrity and/or airworthiness is always an important designconsideration.

The following figures show a tilt rotor system embodiment and a (main)wing embodiment prior to attachment of the tilt rotor system to thewing.

FIG. 2A is a diagram illustrating an embodiment of a tilt rotor systemprior to attachment to a wing. In this example, the exemplary tilt rotorsystem is configured to be attached to the trailing edge of a main wing.For example, inboard tilt rotor 102 from FIG. 1 may be implemented asshown. The outboard tilt rotors (e.g., tilt rotor 120 in FIG. 1) or thecanard tilt rotors (e.g., tilt rotor 106 in FIG. 1) may be implementedwith some modifications to accommodate the slightly different attachmentpoints or interfaces. In this example, the rotor portion (200) of thetilt rotor system is in a vertical flight mode (i.e., pointingdownward).

The pylon portion (202) of the tilt rotor system is used to attach thetilt rotor system (at least in this example) to the exposed aft spar(not shown here) of a (main) wing. In this example, the pylon portionincludes an opening or interface at the distal end of the pylon portion(202) opposite the rotor portion (200) that is designed to fit aroundthe main wing. The surfaces exposed in this part of the pylon include anupper contacting surface (204) as well as a lower contacting surface(206) that fit against the upper surface and lower surface of the mainwing (not shown), respectively, when the tilt rotor system and wing arecoupled or otherwise attached.

In this example, there is also a vertical contacting surface (208) whichcomes into contact with some vertical surface of the main wing.Naturally, in some embodiments this surface is excluded. For example,the main wing may taper to a point such that the pylon and the main winghave a V-shaped interface. In that case, the upper contacting surfaceand lower contacting surface of the pylon section would meet in a Vwithout any intervening contacting surface, such as vertical contactingsurface (208). In some embodiments, the pylon and the main wing may havea more rounded, U-shaped interface where the upper and lower contactingsurfaces curve into each other. The design of the wing-pylon interfaceand associated surfaces that come into contact with each other may varydepending upon the application, vehicle materials, and/or designobjectives.

As shown in this example, in some embodiments, a tilt rotor systemincludes a pylon portion that includes an upper contacting surface thatis configured to be in contact with an upper surface of a wing when thetilt rotor system and the wing are coupled. The pylon portion alsoincludes a lower contacting surface that is configured to be in contactwith a lower surface of the wing when the tilt rotor system and the wingare coupled. The tilt rotor system further includes a rotor portion thatincludes a rotor, where the rotor portion is moveably coupled to thepylon portion such that the rotor portion is able to move between: (1) afirst position that is associated with a vertical flight mode of avehicle that includes the tilt rotor system and the wing and (2) asecond position that is associated with a forward flight mode of thevehicle that includes the tilt rotor system and the wing.

FIG. 2B is a diagram illustrating an embodiment of a wing prior toattachment of a tilt rotor system. For example, the main wing (104) inFIG. 1 may be implemented as shown before the various tilt rotors areattached. In the example of FIG. 1, the exemplary eVTOL vehicle isdesigned to be relatively lightweight in order to extend range and/orbattery life. For context, the example vehicle shown in FIG. 1 weighswithin a range of 350-450 kg. As such, the exterior of the aircraft(including the exterior of the main wing) is made of a compositematerial which is lighter than other materials (e.g., it is lighter thana metal airframe). To provide structural support, the main wing in thisexample has two continuous spars (220 b and 222 b) which extend from thetip of the wing shown, through the fuselage (not shown).

In this example, the wing has two gaps or exposed sections (224 and 226)which the pylons of the tilt rotors fit into (not shown) and whichexpose the aft spar (220 b) to the pylon so that the pylon is in contactwith the aft spar when the tilt rotor system is attached. Although notshown from this view, the spars extend vertically inside the main wingfrom the top interior surface to the bottom interior surface. Theexposed sections of the aft spar therefore present vertical surfaces forthe pylons to come into contact with and match or otherwise correspondto the vertical contacting surface (208) shown in FIG. 2A. Structurally,it may be desirable to have the pylon (and thus the tilt rotor system)be in direct (or practically direct) contact with the (exposed) aft spar(as shown here) as opposed to having the pylon attach to (only)composite material which may flex or bend and in general is less stable.

As described above, in this example the wing is at least partially madeof composite material. In some embodiments, the two gaps or two exposedsections (224 and 226) are created by forming the composite material insegments, leaving spaces or gaps between segments. This may produce astronger and/or more secure connection between the tilt rotor systemsand the canard or wing.

The following figures show the exemplary tilt rotor system and exemplarywing after they are coupled to each other.

FIG. 2C is a diagram illustrating an embodiment of a top view of a mainwing with tilt rotors attached. In the state shown here, all of the tiltrotors have been attached to the vehicle. As shown here, the inboardtilt rotors (240 c and 242 c) are attached to the main wing in such away that the pylon's opening wraps around the aft spar (220 c). Invarious embodiments, the tilt rotors are secured using an adhesive onthe surface(s) where the pylon comes into contact with the main wing orcanard, and/or by adding one or more layers of composite where the pylonmeets the main wing or canard. As described above, having the pylonswrap around the main wing, and more specifically, around an aft sparwhich is one of the strongest parts of the main wing, as shown here mayimprove the airworthiness and/or structural stability of the vehiclecompared to previous versions of the vehicle that attached the tiltrotors using a elliptically-shaped cutout in the wing and anelliptically-shaped pylon.

FIG. 2D is a diagram illustrating an embodiment of an angled view of amain wing with tilt rotors attached. The systems shown in FIG. 2C andFIG. 2D are in the same state (e.g., of assembly) but shown fromdifferent angles. From this view, both the forward spar (222 d) and theaft spar (220 d) are visible within the main wing (264). The openings ofthe pylons of the inboard tilt rotors (240 d and 242 d) wrap around themain wing (264). As described above, the pylons of the tilt rotors arein contact with and/or flush against the aft spar (220 d), which permitsa more secure and/or stronger interface between the inboard tilt rotors(240 d and 242 d) and the main wing (264).

For convenience, the above example shows a complete tilt rotor system.In practice, various components may be attached and/or built up in anysequence or order as desired. For example, if desired, only the pylonsof the tilt rotors (e.g., without the rotor portion and internalcomponents) may be attached to the canard and main wing. The pylonwithout the rotor and internal components is much lighter, making iteasier to align and bond to the wing, which saves costs in terms ofequipment needed for integration and time for setting up the bond.Subsequently, the rotor portion of the tilt rotor system and internalcomponents are attached to the pylon portion.

In addition to and/or as an alternative to improved features associatedwith attaching tilt rotors to the main wing or canard, internalcomponents within the tilt rotor system may be arranged in a manner thattakes into account thermal dissipation. The following figures show anexample of this.

FIG. 3A is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a forward flight position. In this example, thepylon portion (300 a) of this tilt rotor system is configured to beattached to the end of a (main) wing. For example, the outboard tiltrotor (120) shown in FIG. 1 may be implemented as shown. A canard tiltrotor may be implemented similarly and for brevity is not describedherein. For reference, the cross sections of the aft spar (302) and mainwing (304) are indicated. For clarity and readability, some internalcomponents within the tilt rotor system are not necessarily shown here.

To help the vehicle's aerodynamics, one function of the pylon portion(300 a) is to create beneficial separation between the (trailing edge ofthe) main wing (304) and the rotor blades (316 a). In this specificexample, the distance between the trailing edge of the main wing (304)and the rotor blades (316 a) when in forward flight position is in therange of 530-570 mm. This range is to allow a desirable and/or optimalcenter of thrust location from the propellers in hover position whilestill allowing a desirable and/or optimal aerodynamic center locationfrom the main wing in forward flight.

In this example, the components in the tilt rotor system are air cooled.Air enters the tilt rotor system via an intake air vent (306 a) that islocated on the bottom surface of the pylon. The air first flows througha heat sink (308 a) which is used to dissipate heat from a rotor (motor)controller (not shown) which is located in the pylon and which is usedto control the rotor (motor) 310 a. In this example, the battery whichis used to power the rotor (310 a) is stored in the fuselage andtherefore the heat sink (308 a) in the pylon is not used to dissipateheat from the battery. The heat sink (308 a), rotor controller, and/orother (e.g., electronic) components in this example are mounted orotherwise attached to the pylon vertically (e.g., on a vertical mountingsurface inside the pylon which is accessible via an access panel on theside of the pylon).

The air (which has removed at least some heat from the heat sink (308a)) then exits the pylon portion (300 a) and enters the rotor portion(312 a) of the tilt rotor system. The rotor (310 a) is typically hotterthan the heat sink (308 a) and so arranging the components as shown here(with the air first coming into contact with the heat sink andsubsequently the rotor) permits the heat to be dissipated from bothcomponents. It would be undesirable, for example, if the air (heating byfirst coming into contact with the motor, not shown here) were hotterthan the heat sink and caused heat to transfer from the heated air tothe heat sink.

After passing through the rotor (310 a), the air exits the rotor portion(312 a) of the tilt rotor via an exhaust vent (314 a) at the tapered endof the rotor portion.

FIG. 3B is a diagram illustrating an embodiment of a tilt rotor system,including ductwork and streamlines, in a forward flight position. Inthis diagram, streamlines are shown to illustrate how the air enters andexits the exemplary tilt rotor system. As described above, air entersthe tilt rotor system via the intake air vent (306 b) on the bottomsurface of the pylon (300 b). The air then passes through the heat sink(308 b) and exits through an opening in the rear of the pylon. Some ofthe air then enters the rotor portion (312 b) while some air exits thetilt rotor system entirely (note, for example, the streamlines in thepocket formed by the pylon portion (300 b) and the rotor portion (312b)). Within the rotor portion (312 b), the air flows through the rotor(310 b) before exiting through the exhaust vent (314 b).

FIG. 3C is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a forward flight position viewed at an angle. Inthis diagram, the exemplary tilt rotor system is shown at an angle tobetter show some other features and/or aspects of the exemplary tiltrotor system. For example, in this diagram, the access panel (350) whichprovides access to the interior of the pylon and which is located on theside of the pylon is better shown. The access panel does not extendentirely to the front of the pylon. Rather, there is a forward portion(352) of the pylon (including, for context, the intake air vent (306 c)and horizontal duct (354)) which is located forward relative to the sideaccess panel. An air chamber (356), which guides the air through thefins of the heat sink (308 c), follows the horizontal duct (354). Asshown in this diagram, the air chamber (356) is adjacent to and/orexposed by the access panel (350) when the access panel is open. In someembodiments, this chamber is attached to the cover or housing (358)which includes the rotor controller, avionics, and/or other (electronic)components. In some other embodiments, this chamber is attached to theinterior surface of the access panel (350).

As shown in this example, in some embodiments the pylon portion furtherincludes an intake air vent and a heat sink, wherein air from the intakeair vent in the pylon portion cools the heat sink in the pylon portionbefore cooling the motor in the rotor portion when the rotor portion isin the second position that is associated with the forward flight mode,and the intake air vent is disposed on a bottom surface of the pylonportion and the heat sink is attached vertically inside the pylonportion.

The following figures show the exemplary tilt rotor described above butin a hovering and/or vertical flight mode.

FIG. 4A is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a vertical flight position. As described above,the pylon portion (400 a) of the exemplary tilt rotor system isstationary (e.g., relative to the aft spar (402) and main wing (404))whereas the rotor portion (412 a) of the tilt rotor system rotatesbetween a vertical or hovering mode or position (shown here) and aforward flight mode or position (shown above). As such, while the intakeair vent (406 a) and heat sink (408 a) are in the same position whencompared to the above examples, the rotor portion (412 a) (whichincludes rotor (motor) 410 a and exhaust vent (414 a)) is rotatedrelative to the examples described above.

FIG. 4B is a diagram illustrating an embodiment of a tilt rotor system,including ductwork and streamlines, in a vertical flight position. Inthe position shown here, the airflow differs from the example describedabove due to the downward-tilted rotor portion (412 b). Similar to theabove example, air enters through intake air vent (406 b) on the bottomsurface of the pylon (400 b). The air then passes through the heat sink(408 b) and exits through an opening (420) in the rear of the pylon.Unlike the above example, however, all of the air from the pylon portiondoes not enter the rotor portion (412 b) and pass through the rotor (410b) but rather exits the tilt rotor entirely and is drawn down throughthe blades of the rotor.

It is noted that the streamlines shown here only reflect the air thatenters via the intake air vent. Other air (not shown) may enter therotor portion (412 b) and pass through the rotor (410 b) to cool therotors before exiting through the exhaust vent (414 b). For example, asFIG. 3C shows, the rotor may be exposed to permit airflow and coolingeven when the rotor portion (412 b) is positioned for vertical flight.The back of the rotor portion is almost fully exposed in vertical flightand open to ambient air, which helps cooling.

FIG. 4C is a diagram illustrating an embodiment of a tilt rotor system,including ductwork, in a vertical flight position viewed at an angle. Asin the previous example, the access panel (450), forward portion (452)of the pylon, and intake air vent (406 c) which feeds into horizontalduct (454) which in turn feeds into the air chamber (456) whichsurrounds the heat sink (408 c) which is coupled to the cover or housing(458) of the rotor controller, avionics, and/or other components shown.

The following figures describe another tilt rotor embodiment with adifferent configuration and/or arrangement of components.

FIG. 5A is a diagram illustrating an embodiment of a tilt rotor systemwith an intake air vent on the top surface of the pylon. In thisexample, an outboard tilt rotor system is shown. As with the previousexample, the pylon portion (500 a) of the tilt rotor system isconfigured to fit around a main wing (e.g., flush with, against, and/orotherwise in contact with an exposed spar). But in contrast with theprevious example, the intake air vent (502 a) in this example is locatedon the top surface of the pylon, not the bottom surface.

Depending upon the application and/or design objectives, oneconfiguration may be more desirable and/or attractive than the other.For example, having an intake air vent on the bottom surface of thepylon may be desirable in situations where duct size must be minimizedfor drag reduction at higher speeds, as the lower surface sees higherambient static pressure in flight. It has a further advantage ofproviding some limited protection from moisture ingress in rainyconditions.

In contrast, having the intake air vent on the top surface may bedesirable when operations are conducted from unprepared surfaces whichresults in a large amount of debris being kicked up by the propwashduring takeoff and landing, since the wing provides some degree ofprotection.

The exemplary tilt rotor system shown here is also slightly longer andslightly wider to fit more powerful components allowing more payload tobe lifted while still retaining aerodynamic efficiency. The additionallength also allows installation of larger diameter rotors, which aremore efficient. In this specific example, the distance between thetrailing edge of the main wing and the rotor blades (not shown) when inforward flight position is 500-650 mm where the range allows a desiredand/or optimal center of thrust location from the propellers in hoverwhile still allowing a desired and/or optimal aerodynamic centerlocation from the main wing in forward flight. It is noted the vehicleas whole underwent development and/or changes, not just the tilt rotorsystem, resulting in a slightly different range of desired and/oroptimal distances. As shown collectively in this example and the examplefrom FIGS. 3A-4C, in some embodiments, a tilt rotor system is configuredto position a blade associated with the rotor within a range of 500-650mm that is measured from the wing when the rotor portion is in a(second) position that is associated with a forward flight mode. Asdescribed above, in some embodiments, the desired distance of theblade(s) is based at least in part on (1) an optimal center of thrustlocation when the rotor portion is in the second position that isassociated with the forward flight mode and (2) an optimal aerodynamiccenter location when the rotor portion is in the first position that isassociated with the vertical flight mode.

The rotor portion (504 a) of the tilt rotor system is substantially thesame as in the previous example and for brevity is not described herein.

FIG. 5B is a diagram illustrating an embodiment of a tilt rotor systemwith components horizontally attached inside the pylon. In this example,the heat sink (506 b) and housing (508 b), which includes the rotorcontroller, avionics, and/or other (electronic) components, are mountedor otherwise attached to the pylon portion (500 b) horizontally.Attaching or otherwise placing the components horizontally as shown heremay be preferred in some applications for a variety of reasons. Forexample, the dimensions of the pylon portion (500 b) and the totaldimensions of the heat sink (506 b) and housing (508 b) may be bettersuited to the horizontal placement as shown here (e.g., the pylonportion (500 b), heat sink (506 b), and housing (508 b) are shorter thanthey are taller). Or, given that the aft spar (not shown) is laid outhorizontally and the mouth of the pylon fits around the spar, the heatsink (506 b) and housing (508 b) may fit inside the available interiorspace of the pylon (e.g., the upper protruding section of the pylon)better when laid out horizontally. In some applications, a verticalmounting surface may be preferred for structural reasons (e.g., theprimary forces and moments of concern that act on the tilt rotor systemare in the vertical direction and the vertical mounting surface may actas (additional) reinforcement).

In this particular vehicle and/or application, the components inside thepylon went from a vertical mounting to a horizontal mounting forstructural reasons (e.g., needed more horizontal stiffness than thevertical arrangement could provide) as well as improved aerodynamics(e.g., the arrangement shown here allows a relatively smaller verticalcross-section height exposed to incoming airflow at the point ofattachment to the wing thereby lowering the aerodynamic drag at thejunction by embedding the front of the pylon into the wing's curvedupper surface).

The following figure shows the airflow which enters via the intake airvent (502 b) on the top surface of the pylon portion (500 b) of the tiltrotor.

FIG. 5C is a diagram illustrating an embodiment of a tilt rotor systemwith components horizontally attached inside the pylon and streamlinesshown. In this example, air enters the tilt rotor system via the intakeair vent (502 c) that is disposed on the top surface of the pylonportion (500 c). The air first passes over and removes heat from theheat sink (506 c) which dissipates heat from components (e.g., the rotorcontroller, avionics, etc.) inside the housing (508 c). The air thenexits the pylon portion (500 c) of the tilt rotor system and enters therotor portion (504 c) to cool the rotor (510 c). As described above, theheat sink (506 c) tends to be cooler than the rotor (510 c) so arrangingthe components as shown here (e.g., with the rotor downstream of theheat sink) is desirable because heat can be removed from both.

As shown in this example, in some embodiments, the pylon portion furtherincludes an intake air vent and a heat sink, wherein air from the intakeair vent in the pylon portion cools the heat sink in the pylon portionbefore cooling the motor and/or rotor in the rotor portion when therotor portion is in the second position that is associated with theforward flight mode, and the intake air vent is disposed on a topsurface of the pylon portion, and the heat sink is attached horizontallyinside the pylon portion.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A tilt rotor system, comprising: a pylon portionthat includes: an upper protrusion that is configured to be in contactwith an upper surface of a wing when the pylon portion and the wing arecoupled such that the pylon portion and a rotor portion protrude aft ofthe wing; a lower protrusion that is configured to be in contact with alower surface of the wing when the pylon portion and the wing arecoupled such that the pylon portion and the rotor portion protrude aftof the wing; an intake air vent; a horizontal surface that is in ahorizontal position when the wing and the pylon portion are coupled suchthat the pylon portion and the rotor portion protrude aft of the wing; arotor controller that is coupled to the horizontal surface; and a heatsink that is coupled to the horizontal surface and that is configured todissipate heat from at least the rotor controller; and the rotorportion, wherein: the rotor portion is moveably coupled to the pylonportion such that one or more rotor blades included in the rotor portionare able to move between: (1) a first position below the wing that isassociated with a vertical flight mode of a vehicle that includes thetilt rotor system and the wing and (2) a second position aft of the wingthat is associated with a forward flight mode of the vehicle thatincludes the tilt rotor system and the wing; and the rotor portionincludes a rotor that is controlled by the rotor controller in the pylonportion, wherein: heat sink heated air is produced by fresh air enteringthe intake air vent in the pylon portion and being heated by the heatsink in the pylon portion; the heat sink heated air flows from the pylonportion to the rotor portion; and the heat sink in the pylon portion iscooler than the rotor in the rotor portion such that the heat sinkheated air is able to cool the rotor in the rotor portion when the heatsink heated air flows by the rotor in the rotor portion because the heatsink heated air is cooler than the rotor in the rotor portion.
 2. Thetilt rotor system of claim 1, wherein the tilt rotor system isconfigured to position a blade associated with the rotor within a rangeof 500-650 mm from the wing when the rotor portion is in the secondposition that is associated with the forward flight mode.
 3. The tiltrotor system of claim 1, wherein the tilt rotor system is configured toposition a blade associated with the rotor within a desired range fromthe wing when the rotor portion is in the second position that isassociated with the forward flight mode, wherein the desired range isbased at least in part on (1) an optimal center of thrust location whenthe rotor portion is in the second position that is associated with theforward flight mode and (2) an optimal aerodynamic center location whenthe rotor portion is in the first position that is associated with thevertical flight mode.
 4. The tilt rotor system of claim 1, wherein: theintake air vent is disposed on a bottom surface of the pylon portion;and the heat sink is attached vertically inside the pylon portion. 5.The tilt rotor system of claim 1, wherein: the intake air vent isdisposed on a top surface of the pylon portion; and the heat sink isattached horizontally inside the pylon portion.
 6. The tilt rotor systemof claim 1, wherein the wing is at least partially made of a compositematerial.
 7. The tilt rotor system of claim 1, wherein the pylon portionfurther includes a vertical contacting surface that is configured to bein contact with a vertical surface of an exposed spar included in thewing when the tilt rotor system and the wing are coupled.
 8. A method,comprising: providing a pylon portion associated with a tilt rotorsystem, wherein the pylon portion includes: an upper protrusion that isconfigured to be in contact with an upper surface of a wing when thepylon portion and the wing are coupled such that the pylon portion and arotor portion protrude aft of the wing; a lower protrusion that isconfigured to be in contact with a lower surface of the wing when thepylon portion and the wing are coupled such that the pylon portion andthe rotor portion protrude aft of the wing; an intake air vent; ahorizontal surface that is in a horizontal position when the wing andthe pylon portion are coupled such that the pylon portion and the rotorportion protrude aft of the wing; a rotor controller that is coupled tothe horizontal surface; and a heat sink that is coupled to thehorizontal surface and that is configured to dissipate heat from atleast the rotor controller; and providing the rotor portion, wherein:the rotor portion is moveably coupled to the pylon portion such that oneor more rotor blades included in the rotor portion are able to movebetween: (1) a first position below the wing that is associated with avertical flight mode of a vehicle that includes the tilt rotor systemand the wing and (2) a second position aft of the wing that isassociated with a forward flight mode of the vehicle that includes thetilt rotor system and the wing; and the rotor portion includes a rotorthat is controlled by the rotor controller in the pylon portion,wherein: heat sink heated air is produced by fresh air entering theintake air vent in the pylon portion and being heated by the heat sinkin the pylon portion; the heat sink heated air flows from the pylonportion to the rotor portion; and the heat sink in the pylon portion iscooler than the rotor in the rotor portion such that the heat sinkheated air is able to cool the rotor in the rotor portion when the heatsink heated air flows by the rotor in the rotor portion because the heatsink heated air is cooler than the rotor in the rotor portion.
 9. Themethod of claim 8, wherein the tilt rotor system is configured toposition a blade associated with the rotor within a range of 500-650 mmthat is measured from the wing when the rotor portion is in the secondposition that is associated with the forward flight mode.
 10. The methodof claim 8, wherein the tilt rotor system is configured to position ablade associated with the rotor within a desired range that is measuredfrom the wing when the rotor portion is in the second position that isassociated with the forward flight mode, wherein the desired range isbased at least in part on (1) an optimal center of thrust location whenthe rotor portion is in the second position that is associated with theforward flight mode and (2) an optimal aerodynamic center location whenthe rotor portion is in the first position that is associated with thevertical flight mode.
 11. The method of claim 8, wherein: the intake airvent is disposed on a bottom surface of the pylon portion; and the heatsink is attached vertically inside the pylon portion.
 12. The method ofclaim 8, wherein: the intake air vent is disposed on a top surface ofthe pylon portion; and the heat sink is attached horizontally inside thepylon portion.
 13. The method of claim 8, wherein the wing is at leastpartially made of a composite material.
 14. The method of claim 8,wherein the pylon portion further includes a vertical contacting surfacethat is configured to be in contact with a vertical surface of anexposed spar included in the wing when the tilt rotor system and thewing are coupled.